Replacement of dicalcium phosphate by rock phosphate in cattle diets: nutrients digestibility, plasma parameters, ruminal fermentation and microbial synthesis efficiency

Abstract

-This study was conducted in order to evaluate the effects of replacing dicalcium phosphate by rock phosphate in diets of growing steers. It was determined the following aspects: apparent digestibility of diets; phosphorus (P), calcium and fluorine apparent absorption; ruminal pH; ruminal ammonia concentration; microbial efficiency and plasma P.Five rumen fistulated Holstein steers weighting 275 -283 kg were used. Experimental design was a 5 × 5 Latin square and diets consisted of 0, 25, 50, 75 and 100% of dicalcium phosphate replacement by rock phosphate in the mineral supplement. Addition of rock phosphate in the diets produced a linear increase on intake, rumen outflow and fecal output and total disappearance of fluorine. Diets did not differ to apparent absorption of calcium as well as dry matter, organic matter, crude protein, neutral detergent fiber and non-fiber carbohydrates intake, excretion, digestion and partial and total apparent digestibility. Plasma phosphorus was not influenced by diets and the average was 5.93 mg/dL. There was no difference for ruminal pH and ruminal ammonia concentration. Dicalcium phosphate replacement did not affect apparent and true protein microbial synthesis. Total replacement of dicalcium phosphate by rock phosphate in growing steer mineral supplement did not affect ruminal environment and protein synthesis in rumen. Considering this, dicalcium phosphate replacement in growing steer diets decreases P absorption and depending on its requirements it should be carefully seen.Key Words: phosphorus sources, plasma phosphorus, rumen microbial protein, ruminal fermentation Substituição de fosfato bicálcico pelo fosfato de rocha em dieta para bovinos: digestibilidade dos nutrientes, parâmetros plasmáticos, fermentação ruminal e eficiência de síntese microbiana RESUMO -Este estudo foi conduzido para avaliar os efeitos da substituição do fosfato bicálcico pelo fosfato de rocha na dieta de bovinos em crescimento. Foram determinados a digestibilidade aparente das dietas, a absorção aparente do fósforo, cálcio e flúor, o pH ruminal, a concentração de amônia ruminal, a eficiência microbiana e o fósforo no plasma utilizando-se cinco bovinos da raça Holandesa Preto-e-Branco, fistulados, pesando entre 275 e 283 kg. O delineamento estatístico foi um quadrado latino 5 × 5 e as dietas consistiram de 0, 25, 50, 75 e 100% de substituição do fosfato bicálcico pelo fosfato de rocha no suplemento mineral. A adição de fosfato de rocha nas dietas ocasionou aumento linear na ingestão, no fluxo omasal, no fluxo fecal e no desaparecimento total do flúor. As dietas não diferiram quanto à absorção aparente do cálcio, assim como em relação à ingestão, excreção, digestão e digestibilidades aparentes parcial e total da matéria seca, matéria orgânica, proteína bruta, fibra em detergente neutro e carboidratos não-fibrosos. O fósforo no plasma não foi influenciado pelos tratamentos e a média foi de 5,93 mg/dL. Não houve diferença para o pH ruminal e concentração de amônia ruminal. A substituição do fo...

Nutrient absorption in lambs fed diets containing different amounts of phosphorus

“…The digestibility coefficient of OM, with an average of 0.61±0.028, was similar to that found by Coneglian et al (16) in steers, with an average value of 0.66.…”

“…Although there are not many studies that evaluate the digestibility of nutrients when providing different amounts of P, there is evidence that indicates that organic matter (OM) digestibility is usually not affected, if there is no P deficit (15,16). On the contrary to what happened in the present study, the authors found that the coefficient of absorption of the NDF fraction (50% of the diet) in adult sheep (38-43 kg) was affected (p<0.05) by variations in the P levels (up to 8 g P/day).…”

Development of Candelilla Wax Oleogels as a Medium of Controlled Release of Phosphorus in an In Vitro Model

“…On the other hand, in highly developed countries that supplement animal feed with high amounts of minerals, pollution increases because excess minerals are secreted [4]. For example, US dairy producers use feed that exceeds the Nutrient Requirements of Dairy Cattle dietary phosphorus recommendations by 45-50% [5,6]. For this reason, controlled mineral supplementation alternatives should be sought to avoid both mineral deficiency and overload.…”